When the AOA vane that MCAS was using was working properly, MCAS probably also worked fine; it was when that single AOA vane went bad, probably indicating “full-scale high” that MCAS would drive the airplane into the ground.
That was a colossal human failure of the highest order.
It is hard to take you seriously when you make exaggerated statements. As an aviation control expert you should be well aware that “runaway trim” has been an issue from various causes since electric trim assist was first devised who knows how many decades ago. That is why there are cutout switches right next to the trim wheel of every airplane that I am aware of that has it. And this is true even for airplanes that don't have a computer “helping” the pilots.
A sticky solenoid, a short circuit, a bad switch or sensor can all cause the problem. Are solenoids that malfunction, wires that have bad connections, or sensors that have bad sending units colossal human failures as well? All the nonsense from self appointed non-flier experts with no historical perspective is the reason I stopped commenting on this issue months ago. Thanks for reminding me.